SyntaxError: "x" is a reserved identifier
The JavaScript exception "variable is a reserved identifier" occurs when reserved keywords are used as identifiers.
Message
SyntaxError: Unexpected reserved word (V8-based) SyntaxError: implements is a reserved identifier (Firefox) SyntaxError: Cannot use the reserved word 'implements' as a variable name. (Safari)
Error type
What went wrong?
Reserved keywords will throw in if they are used as identifiers. These are reserved in strict mode and sloppy mode:
enum
The following are only reserved when they are found in strict mode code:
implements
interface
let
package
private
protected
public
static
Examples
Strict and non-strict reserved keywords
The enum
identifier is generally reserved.
js
const enum = { RED: 0, GREEN: 1, BLUE: 2 };
// SyntaxError: enum is a reserved identifier
In strict mode code, more identifiers are reserved.
js
"use strict";
const package = ["potatoes", "rice", "fries"];
// SyntaxError: package is a reserved identifier
You'll need to rename these variables.
js
const colorEnum = { RED: 0, GREEN: 1, BLUE: 2 };
const list = ["potatoes", "rice", "fries"];
Update older browsers
If you are using an older browser that does not yet implement
let
or
class
,
for example, you should update to a more recent browser version that does support these
new language features.
js
"use strict";
class DocArchiver {}
// SyntaxError: class is a reserved identifier
// (throws in older browsers only, e.g. Firefox 44 and older)